In recent years, in the field of automobiles, air vehicles and the like, in order to detect an obstacle located ahead in a travel direction with a high degree of accuracy, a laser scanning type measuring machine which obtains information of the obstacle on the basis of a relationship between laser light externally emitted and reflected light striking the obstacle to be reflected (or the reflected light striking a structure after passing through the object to return) is developed to be already in practical use.
In a general laser scanning type measuring machine, a light projecting system is formed of a laser diode and a collimator, and a light receiving system is formed of a light receiving lens (or a mirror) and a light detecting element such as a photodiode. A reflecting mirror provided with a reflecting surface is further arranged between the light projecting system and the light receiving system. Such laser scanning type measuring machine reflects the light emitted from the light projecting system by a rotating reflecting surface by rotation of the reflecting mirror and irradiates in a direction in which detection of the object is desired. This is advantageous in that this may measure the object in a wide range in a two-dimensional manner instead of measuring at one point.
A motor or the like is used as a power source for rotating the reflecting mirror for laser light scanning. On the other hand, there also is a request to make the reflecting mirror of resin in order to reduce cost and weight. Therefore, a manner of connecting the reflecting mirror made of resin to a rotary shaft of the motor or the like poses a problem.
Herein, in a case where the reflecting mirror is connected to a rotary shaft of the motor or the like, it is also conceivable to divert a technology of a polygonal mirror used in, for example, a copying machine or the like. As a fixing method of the polygonal mirror, a method of screwing a polygonal mirror to a flange (step) provided on the rotary shaft in a state in which the former is fitted to be mounted on the latter. However, if the polygonal mirror is made of resin, the reflecting surface might be deformed by screwing, which leads to deterioration in accuracy of detection of the object.
On the other hand, Patent Literature 1 discloses a technology of avoiding distortion of a lens surface as much as possible by allowing a projection provided on a flange of an elongated fθ lens to abut a lens holding member to hold.